The preparation of polyether carbonate polyols by catalytic reaction of alkylene oxides (epoxides) and carbon dioxide in the presence of H-functional starter substances (“starters”) has been the subject of intensive study for more than 40 years (e.g. Inoue et al., Copolymerization of Carbon Dioxide and Epoxide with Organometallic Compounds; Die Makromolekulare Chemie 130, 210-220, 1969). This reaction is shown in schematic form hereinbelow, where R is an organic radical such as alkyl, alkylaryl or aryl, each of which may also contain heteroatoms, for example O, S, Si etc., and where e, f and g are integers, and where the product shown here in the scheme for the polyether carbonate polyol should merely be understood such that blocks having the structure shown may in principle be present in the polyether carbonate polyol obtained, but the sequence, number and length of the blocks and OH functionality of the starter can vary, and is not limited to the polyether carbonate polyol shown in the scheme. This reaction is environmentally very advantageous since this reaction constitutes the conversion of a greenhouse gas such as CO2 to a polymer. A further product, actually a by-product, formed is the cyclic carbonate shown in the scheme (for example, when R═CH3, propylene carbonate).

To further increase the sustainability of the obtained polyether carbonate polyols it would be desirable to make H-functional starter substances (“starters”) not based on fossil raw materials available for the process. A substance class readily accessible from natural products are carboxylic acids. For example, malic acid, succinic acid, lactic acid and citric acid are readily accessible by fermentation. A process for enzymatic preparation of 5-norbornene-2-carboxylic acid is described in Eur. J. Biochem. 182, 349-356, 1989. A fermentative process for preparing 5-norbornene-2-carboxylic acid is described in WO 2007071578 A2. Readily accessible natural products further include amino acids which likewise contain a carboxylic acid group.
Double metal cyanide compounds are particularly suitable as catalysts for preparing polyether carbonate polyols by catalytic reaction of alkylene oxides (epoxides) and carbon dioxide in the presence of H-functional starter substances (“starters”).
WO-A 2008/092767 discloses a process for preparing polyether carbonate polyols, characterized in that one or more H-functional starter substances are initially charged in the reactor and in that one or more H-functional starter substances are metered continuously into the reactor during the reaction. Recited alkoxylation-active groups having active H atoms also include CO2H.
EP 2703425 A1 discloses a process for preparing polyether carbonate polyols by addition of alkylene oxides and carbon dioxide onto one or more H-functional starter substance(s) in the presence of a double metal cyanide catalyst, characterized in that a suspension medium containing no H-functional groups is initially charged in a reactor and one or more H-functional starter substance(s) are metered continuously into the reactor during the reaction. Disclosed monofunctional starter substances also include carboxylic acids (monofunctional carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid and fatty acids such as stearic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid and also benzoic acid and acrylic acid).
Double metal cyanide catalysts suitable for catalytic reaction of alkylene oxides (epoxides) and carbon dioxide are characterized by a certain basicity. None of the abovementioned documents disclose how upon addition of carboxylic acid a neutralization of the basicity and a reduced activity/a deactivation of the employed DMC catalyst may be avoided.